Generally, a compact camera module installed in the mobile phone for use is structured to drive a lens using a stepping motor, a voice coil motor and a piezoelectric motor for the purpose of adjusting focus and changing a magnification percentage. The aforementioned structure is so complicated that the size reduction is limited, resulting in disadvantage of cost increase. A compact camera module is disclosed in Japanese Unexamined Patent Application Publication No. 2003-111458, which employs a shape-memory actuator with simple structure and compact size for cost reduction. The aforementioned actuator is structured to bring a center curved portion of the U-like shape-memory-alloy in contact with a lens guide portion provided at one side of a lens holder, and slidably move the lens holder along the guide under the heat resulting from current application.
The related art disclosed in Japanese Unexamined Patent Application Publication No. 2003-111458 is not provided with a mechanism for cooling the actuator, thus deteriorating the response of the actuator to the driving operation during cooling. Direct fixation between the actuator and the printed circuit board via a solder hardly allows flexibility for setting the mount position on the printed board. As a result, the area for installing the camera module is enlarged. Under the heat resulting from current application to the actuator causes thermal expansion of the actuator, thus deteriorating the contact between the actuator and the solder.
Japanese Unexamined Patent Application Publication No. 2009-41545 discloses the structure for sealing the shape-memory-alloy which generates heat and the image pickup device within the lens holder. The heat release of the shape-memory actuator is deteriorated to impair the response during cooling. The temperature of the image pickup device is also increased to raise noise level, resulting in deteriorated image quality.